The present invention relates to zoom lenses, and more particularly to a zoom lens which has a simplified and improved macrophotographing function.
Recently, zoom lens having a so-called "macromechanism" permitting ordinary focusing distance photography and close-up or macro focusing distance photography (macrophotography) has been extensively employed. The conventional zoom lens with a macromechanism uses a special helicoid (helicol groove) in order to increase the amount of extension in the macrophotographing range, and therefore needs some way of switching between the special helicoid and the helicoid for ordinary focusing distance photography. Thus, the conventional zoom lens of this type is considerably intricate in construction and accordingly high in manufacturing cost.
Further, the closest focusing distance of a zoom lens is determined by the focusing distance in the zooming range where "vignetting" (insufficient quantity of surrounding light) occurs most significantly. At other focusing distances, the quantity of surrounding light is sufficient, and hence the closest focusing distance can be decreased. In general, the closest focusing distance is reduced at both ends of the zooming range, that is, the longest focus and the shortest focus positions.